This invention relates to pinch valves and more particularly concerns fluid operated pinch valves in which replacement of the flexible valve sleeve is facilitated without compromise of valve sealing.
Pinch valves or flexible sleeve valves have been employed for many years for their unique capability in handling of slurries, abrasive fluid media and other fluids that may contain solids. In general, such a pinch valve comprises a rigid casing that is fixed in a fluid flow line and contains a flexible sleeve. The sleeve is fixed to and sealed at its ends to the casing and means are provided to selectively compress the intermediate portion of the sleeve between its ends to such an extent that the central portion of the sleeve completely collapses with its interior surfaces in fluid-tight contact with each other to thereby block fluid flow. Such valves may be closed either partly or completely. They may properly close over solids entrained within the flowing fluid and seal fluid flow, leak-free, in spite of the presence of the solids.
For fluid actuation of the valve, a chamber is provided between the valve casing and an intermediate section of the flexible sleeve. Air or some other fluid under pressure is injected into the chamber to balance the internal flowing fluid pressure on the one hand when the valve is open, and to overcome such internal flowing fluid pressure to close the valve when fluid flow is to be prevented.
The nature of the pinch valve is such as to create large forces tending to move the sleeve longitudinally relative to its casing. Thus significant problems exist in properly retaining the flexible sleeve at its end portions while permitting adequate flexibility for closing. The pinch valve sleeve has been provided with an enlarged end flange which fits between the conventional end flange of the valve casing and the mating flange of the flow line to which the valve end flange is bolted. Such an arrangement is effective in both retaining the sleeve longitudinally and sealing the sleeve and casing in the flow line. However, such prior valves require that the entire valve be disconnected and removed from the flow line in order to install or remove the sleeve.
Particularly because of its common use with corrosive materials or abrasive slurries, the flexible sleeve is subject to wear and requires replacement from time to time. The requirement for complete removal of the valve in order to replace the sleeve is burdensome and time consuming and may limit locations and physical arrangements of the valve in a flow line.
In mechanically operated pinch valves sealing is important only between the flexible sleeve and the flow line. In fluid operated valves on the other hand, pressures of actuating fluid in the chambers between the sleeve and the valve casing must be considerably higher than pressure of the fluid flowing through the flow line and thus one must obtain satisfactory sealing of the sleeve to the flow line and to the casing about the fluid actuating portion of the valve. Prior arrangements have not provided adequately sealed fluid operated pinch valves in which the sleeve can be replaced without removing the valve body from the flow line.
Accordingly, it is an object of the present invention to provide a pinch valve that eliminates or minimizes above-mentioned problems.